WRAP8 in AMBA AHB.....means what....?

address wrapping in ahb

Hi all...

what do we mean by WRAP8 or WRAP4 function in AMBA...

I mean if we give starting address as 0X28...for an eight burst WRAP ...

How the sequence will be followed.........?


Thanks

wrap4 in amba

my understanding is that, after the burst has been completed, i.e. after the data is stored in consecutive addresses from 0x28 to 0x30, the starting address for the next transaction will once again loop back to 0x28.

correct me if i'm wrong.

amba ahb burst mode

Understand the wraps are genrallly used to fill the cache lines. Suppose your cache line is 8 words long . Then first line of cache line would have address of
0- 4 - 8 -0xC - 0x10 - 0x14 -0x18 - 0x1C

Suppose the processor wants data in memory location 28 which is not there in the cache. The cache controller will ask for a wrap-8 transaction of 28 (hex-0x1C). Which will cause memory address 28 - 0 - 4 - 8 -12 -16-20 -24 to happen .

If you don't understand the concept of how cache works but simply want to figure out what are the next address it will access to then. For burst-8 when you add 4 to get the next memory access address change only the last (4 + 1) lsb of the address (2 ^ 4 = 8 ). Mail back if you still don't understand.

how is wrap used for cache + ahb

As in the above given explaination by semiconductor man,

suppose the memory address in the cache which are supposed to be used by a particular master(address decoding) are 0- 4 - 8 -0xC - 0x10 - 0x14 -0x18 - 0x1C and the 0- 4 - 8 -0xC and master starts the address from 0x18 for an 8 beat transfer and hence it has to wrap back to either 0 or 0x18(possibily 0) due to inavailable memory.

and this start at 0x18 may be due to a earlier back-back transfer. this one is my gues may be false. And this all depends on the master interface design wher ahb supports these kinds of tranfers. if any thing is awry please correct me.

Thanks & regards

amba wrap 8 burst

what is AHB?

naveen sudhish

use wrap with hsize , it decide where the address shoud wrap, the wrapping period is wrapx * hsize

wrap8

i really dont under stand about WRAPPING mode operation in AMBA AHB pls help

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